The objective of this proposal is to examine the circuitry of luteinizing hormone-releasing hormone (LHRH) neurons in releation to specific neuroeffectors in the central nervous system. This proposal will utilize immunocytochemistry to localize LHRH and study its relationship to neuronal structures containing dopamin beta hydroxylase, serotonin, vasoactive intestinal polypeptide, and acetylcholinesterase. Electrophysiological and behavioral effects of microiontophoretic application of LHRH will be examined and correlated with sites of LHRH projection. Radioreceptor assays for LHRH will be developed to characterize LHRH binding in brain, and to establish the link between sites of LHRH fiber termination and receptor binding. Orthograde transport of labeled amino acids in the retinophypothalamic tract will be studied by autoradiography. The sites of termination of this pathway in the hypothalamus will be studied in relation to LHRH - containing neuronal structures. Light and electron microscopy will enable the analysis of these neuropeptides at the synapse. Simultaneous localization of multiple peptides in combination with a variety of techniques will lead to our understanding of the action of neuropeptides.